1. Related Technical Fields
Related technical fields include power management systems, methods, and programs for in-vehicle devices.
2. Description of the Related Art
Various types of in-vehicle devices have been mounted on vehicles to make drivers and fellow passengers in the vehicle more comfortable. For example, radio receivers for receiving AM broadcast and FM broadcast, TV receivers for receiving telecast signals and displaying an image, audio devices for playing an MD and/or a CD, and/or navigation devices for providing driving guidance for the vehicle may be mounted on the vehicle as in-vehicle devices.
To transfer digital data such as digitized image data, audio data, or computer data among the various types of in-vehicle devices described above, large-capacity and high-speed communication is required. Therefore, the introduction of an in-vehicle network to transfer digital data even in a small space such as within the vehicle has been proposed. For example, the MOST (Media Oriented Systems Transport) system is an example of an in-vehicle network (for example, Japanese Unexamined Patent Application Publication No. 2005-277711). The MOST system has a cyclic network. Various in-vehicle devices such as a navigation device, an audio device, a radio receiver, and an AV amplifier are connected to each other via the network. As a result; for example, digital data output from the audio device is transferred to the AV amplifier through the network and the signal input by the AV amplifier is amplified and output to a speaker.
Further, the MOST system utilizes a network protocol using fiber optics. Importantly, systems such as the MOST system control the power of the entire system collectively instead of turning on/off the power supplied to each of the in-vehicle devices in the system. For example, each in-vehicle device and a power management unit for controlling the power of the system are connected to each other with an LAN or the MOST, and request data for turning on/off the power supplied to each of the in-vehicle devices is transferred from the power management unit, so that all of the connected in-vehicle devices may be turned on or off.